[libre-riscv-dev] [Bug 139] Add LD.X and ST.X? Strided

bugzilla-daemon at libre-riscv.org bugzilla-daemon at libre-riscv.org
Tue Oct 8 13:29:37 BST 2019


--- Comment #50 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
Yeah! Worked out how to use REMAP to do cross product!

It would be 2 instructions: one FMUL and one FMACSUB (just like in the PLX 3D
paper) except that the REMAP Shapes are in-place!

SHAPE0: xdim=3, ydim=1, inv=on, offs=2
SHAPE1: xdim=3, ydim=1, offs=1

These will offset and invert the vectors, giving the sequence 021 and 120 which
can be applied to the two vectors by redirection.  It should work fine either
when SUBVL=3 or when VL=3*N.

If nothing else this can be microcoded to not need any extra special hardware.

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